Multifocal Malignant Proliferating Trichilemmal Tumour: A Diagnostic Imitator Beyond the Scalp

Malignant proliferating trichilemmal tumour (MPTT) is a rare cutaneous adnexal neoplasm arising from the outer root sheath of the hair follicle and represents malignant transformation of a proliferating trichilemmal tumour. It accounts for less than 0.1% of cutaneous malignancies and most commonly presents as a solitary scalp lesion in elderly women.
A 60-year-old male presented with progressively enlarging painful swellings over the scalp and left scapular region. Histopathological examination revealed a dermal epithelial tumour showing marked cytological atypia with abrupt trichilemmal keratinization. Periodic acid–Schiff staining demonstrated diastase-resistant cytoplasmic positivity. Immunohistochemistry showed focal CD34 expression with strong nuclear p53 and increased Ki-67 labeling index.
The findings were diagnostic of malignant proliferating trichilemmal tumour. Multifocal involvement occurring in a male patient is exceedingly rare. Recognition of trichilemmal keratinization and the use of histochemical and immunohistochemical markers are essential to distinguish MPTT from squamous cell carcinoma and guide appropriate management.

Malignant proliferating trichilemmal tumour, scalp, scapular lesion, adnexal tumour.

1. Alshaalan Z, Patel P, Routt E, Ciocon D. Proliferating pilar tumour: Two cases and a review of the literature. J Drugs Dermatol. 2021;20(12):1346. [Google Scholar] [Crossref]

2. Headington JT. Tumors of the hair follicle: A review. Am J Pathol. 1976;85(2):479–514. [Google Scholar] [Crossref]

3. Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation. J Cutan Pathol. 2022;22(9):4759. [Google Scholar] [Crossref]

4. Malignant proliferating trichilemmal tumours treated with radical radiotherapy: A case report and review. BMJ Case Rep. 2017;2017. [Google Scholar] [Crossref]

5. Mastroianni A et al. Malignant proliferating trichilemmal tumors of the scalp: A systematic review. Dermatol Surg. 2021;47(8):1078–1086. [Google Scholar] [Crossref]

6. Sau P, Graham JH, Helwig EB. Proliferating epithelial cysts: Clinicopathological analysis of 96 cases. J Cutan Pathol. 1995;22(5):394–406. [Google Scholar] [Crossref]

7. Ye J, Nappi O, Swanson PE. Proliferating trichilemmal tumor: Clinicopathologic analysis of 76 cases. Mod Pathol. 2004;17(9):1152–1160. [Google Scholar] [Crossref]

8. Weedon D. Skin Pathology. 5th ed. Elsevier; 2021. [Google Scholar] [Crossref]

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