|Year : 2021 | Volume
| Issue : 2 | Page : 317-319
Trichilemmal carcinoma of the scalp: Demystifying anecdote of a rare entity
Archana Shetty, Aparna Muralidhar, Nidha Gaffoor
Department of Pathology, Dr. Chandramma Dayananda Sagar Institute of Medical Education and Research, Ramanagara, Karnataka, India
|Date of Submission||02-May-2021|
|Date of Decision||02-Jun-2021|
|Date of Acceptance||03-Jun-2021|
|Date of Web Publication||29-Dec-2021|
Dr. Nidha Gaffoor
Department of Pathology, Dr.Chandramma Dayananda Sagar Institute of Medical Education and Research, Harohalli, Ramanagara, Karnataka
Source of Support: None, Conflict of Interest: None
Trichilemmal carcinoma (TC) is a rare malignant adnexal neoplasm, falling under the umbrella of tumors with follicular differentiation generally presenting as papulonodular growth with surface ulceration over sun-exposed skin. Histologically, it mimics tumors such as basal cell carcinoma, sebaceous carcinoma, squamous cell carcinoma, and malignant proliferating trichilemmal tumors. As there is a difference of opinion regarding the histopathological criteria for TC, a definitive diagnosis should be confined to cases having the majority of histomorphological findings with immunohistochemical corroboration to help define the clinicopathological behavior of this disease. Rarity, indolent clinical course in spite of local aggressiveness and a good survival rate postexcision further undermine the importance of this unique entity.
Keywords: Hair follicle, immunohistochemistry, skin appendage, World Health Organization
|How to cite this article:|
Shetty A, Muralidhar A, Gaffoor N. Trichilemmal carcinoma of the scalp: Demystifying anecdote of a rare entity. Arch Med Health Sci 2021;9:317-9
| Introduction|| |
Appendageal tumors of skin encompass a group of neoplasms, many of which pose a diagnostic challenge to both pathologists and surgeons. Trichilemmal carcinoma (TC), also known as trichilemmocarcinoma, is one such malignant tumor accounting for <0.005% of adnexal carcinomas., This tumor with follicular differentiation needs special attention, as it has close overlapping morphology with other cutaneous malignancies having different management protocols. The distribution of the lesions tends to suggest that sunlight plays an important role in the development of this malignancy. Unlike other skin cancers, TC has an indolent course and is amenable to curative resection with conventional surgery. With the evolution and the complementary use of immunohistochemistry (IHC) in pathology, tissue diagnosis can now be narrowed, thereby providing a confident diagnosis for the treating surgeon.
We report one such case of a rapidly growing scalp tumor which was suspected to be a squamous cell carcinoma. Histopathological examination with IHC confirmed it to be a TC.
| Case Report|| |
A 65-year-old male presented to our hospital with a painless scalp swelling for 2 years, increasing in size over the past few months. There was no history of trauma or discharge. Local examination revealed a nontender, firm, and swelling over the frontal region of the scalp measuring 7 cm × 6 cm 4 cm with surface ulceration. Skin surrounding the ulcer was erythematous [Figure 1]a. X-ray skull showed a soft tissue swelling well above the underlying bone, ruling out a bony lesion [Figure 1]b.
|Figure 1: (a) 65-year-old male presented with scalp swelling, (b) Plain X-ray (AP and lateral view) scalp. Scalp swelling - white arrow|
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The resected specimen measured 6.5 cm × 6 cm × 4 cm. External surface showed an exophytic growth measuring 5.5 cm × 5.2 cm with surface ulceration. Cut section showed a well-circumscribed gray white lobulated tumor with focal hemorrhagic and cystic areas with grossly uninvolved margins [Figure 2]a.
|Figure 2: (a) Gross image of the excised lesion. Inset: Cut surface of the lesion. (b) Photomicrograph showing lobulated tumor with pushing margin (H and E, ×40). Inset: Tumor arising from the pilosebaceous unit (H and E, ×40). (c) Photomicrograph showing pleomorphic tumor cells with trichilemmal keratinization (H and E, ×400)|
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Microscopy showed a tumor with lobular arrangement and peripheral palisading of keratinocytes. The tumor showed focal epidermal connection and pushing margins at the invasive front [Figure 2]b. Individual cells were pleomorphic with moderate eosinophilic to clear cytoplasm, vesicular nuclei, and prominent nucleoli. Frequent mitoses (10–15/10 high power field), trichilemmal keratinization, foci of cystic change, and occasional multinucleated giant cells were observed. Necrosis was minimal (10%). The intervening stroma was highly vascularized. No perineural/lymphovascular invasion was identified [Figure 2]c.
Periodic Acid-Schiff (PAS) stain demonstrated positivity in the clear cells, suggestive of trichilemmal differentiation (Outer root sheath cells of hair follicle contain glycogen, which is PAS positive) [Figure 3]a and [Figure 3]b. IHC for CD34 showed focal positivity [Figure 3]c. A final diagnosis of TC was conferred.
|Figure 3: (a) Photomicrograph showing tumor cells with clear cytoplasm (H and E, ×400), (b) Photomicrograph showing clear cells with PAS positivity (PAS, ×400), (c) Photomicrograph showing focal CD34 positivity (CD34, ×400). Inset: Photomicrograph showing CD34 positivity of outer root sheath cells (CD34, ×400)s|
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| Discussion|| |
Malignant adnexal tumors of the skin are a group of intriguing tumors, each differing in behavior and malignant potential, with not much concurrence on the standard treatment guidelines. The different histologic entities are based on the source of differentiation: eccrine, apocrine, sebaceous, sweat duct, or ceruminous glands within the skin or follicular cells. With increasing incidence, it is time we enhance our understanding about the histomorphological features to categorize the tumors and bring about uniformity in reporting by following the standard guidelines as given by the World Health Organization (WHO).
TC is a malignant adnexal tumor derived from the outer root sheath of hair follicles, the concept of which was first introduced by Headington in 1976. It occurs in the elderly, predominantly in males as a solitary lesion in sun-exposed areas, especially the head and neck region., Being an outdoor worker, it came as no surprise that sun exposure could have been a contributing factor in our case. It may occur de novo, but is more commonly known to arise from a preexisting tumor of trichilemmal origin like trichilemmomas. Superadded trauma and inflammation are postulated to induce the malignant transformation.
Fine Needle Aspiration Cytology is a quick and inexpensive tool for categorizing palpable lesions. The tumor in our case showed cytological features of dysplastic squamous cells and keratotic debris, suggesting a possibility of squamous cell carcinoma. Although cytology gives good accuracy in determining the nature of lesion, it cannot be diagnostic, especially in tumors of the adnexa. Decisive features can be picked up only on histopathological examination.
De Bin investigated the clinicopathological characteristics and prognostic factors of 26 cases of TC, wherein the size of the tumors ranged from 1 cm–8 cm, with a mean of 2.8 cm. The size of the tumor in our case was 5.5cm, which is larger compared to many reported cases to date. Surface ulceration is one of the common features associated with this tumor, also seen in our case.
[Table 1] summarizes the histomorphological features for the diagnosis of TC and its close differentials. [Table 1] highlights the awareness of using simple available special tissue stains such as PAS in histopathology for narrowing down the differentials as it helps confirm the hair sheath origin of the tumors. The overall histopathological features, complemented by PAS and focal CD34 positivity established a diagnosis of TC in our case.
|Table 1: Differentiating features of trichilemmal carcinoma, malignant proliferating trichilemmal tumor and clear cell squamous cell carcinoma|
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The other tumors to be considered in the differentials are:
Pilomatrical carcinoma: Poorly circumscribed, shows characteristic shadow cells and solid aggregates of immature basaloid cells, the absence of lobular proliferation and presence of brisk mitoses.
Basal Cell Carcinoma: Areas of clear cell change involve only a minor portion of the tumor. The peripheral palisading cells rarely show subnuclear vacuolization which is distinctive of hair follicular differentiation as seen in trichilemmal tumors. Tumor cells show minimal pleomorphism and low-mitotic activity and are Berp4 positive.
Sebaceous carcinoma: Multiple intracytoplasmic lipid-rich vacuoles indenting the nucleus. Trichoblastic carcinoma: Stromal component identical to trichoblastoma and basaloid component with atypia.
Desmoplastic benign trichilemmoma: Infiltrative, but no mitosis and pleomorphism.
A lot of emphasis has been given to the marker CD34 in the differential diagnosis between squamous cell carcinoma and trichilemmal tumors. CD34 positivity indicates trichilemmal differentiation and is negative in the former. However, a few studies have shown MPTT and TC to stain negative for CD34. The researchers interpreted this probability of difference to the increase in loss of CD34 staining as the tumor differentiates from moderate to poor grade.
In spite of an appalling clinical appearance, increased nuclear pleomorphism and the presence of atypical mitoses, TC has a very indolent clinical course with unexceptional metastases, suggesting that cure is possible. The treatment of TC is suggested to be exclusively surgical. Simple excision with 1cm margins is believed to be safe, costefficient, and effective for the treatment of TC.
| Conclusion|| |
TC is a rare adnexal malignancy having an indolent course. The distinct features mentioned in the WHO classification of skin tumors need to be followed uniformly by the reporting pathologists to avoid subjective categorization of this entity under the umbrella of MPTT and to differentiate it from the more aggressive tumors like squamous cell carcinoma.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that the name and initials will not be published and due efforts will be made to conceal the identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]