Early Pilomatrix Carcinoma: A Case Report With Emphasis on Molecular Pathology and Review of the Literature
Pilomatrix carcinoma is a rare adnexal tumor with origin from the germinative matrical cells of the hair follicle. Clinically, it presents as a solitary lesion commonly found in the head and neck region and upper back. The tumors cannot be distinguished by their clinical appearance only and frequently are mistaken for cysts. Histopathologic examination provides the definitive diagnosis in most cases. Such carcinomas are aggressive neoplasms with a high probability of local recurrence and distant metastasis. Assessment of the Wnt signaling pathway components such as β-catenin, lymphoid enhancer-binding factor 1 (LEF-1) and caudal-related homeobox transcription factor 2 (CDX-2) potentially can be used for diagnostic purposes and targeted therapy. Herein, we report a rare and unique case of early pilomatrix carcinoma with intralesional melanocytes. We also review the molecular pathology and pathogenesis of these carcinomas as well as the significance of early diagnosis in their management.
Practice Points
- Clinicians and pathologists should be aware of pilomatrix carcinoma to facilitate early detection.
- Early diagnosis and prompt treatment of pilomatrix carcinoma is crucial in lowering recurrence rate and avoiding a poor outcome.
- Caudal-related homeobox transcription factor 2 and β-catenin components of the Wnt signaling pathway play an important role in the pathogenesis of pilomatrix carcinoma.
- Although controversial, wide local excision is the treatment of choice for pilomatrix carcinoma.
Our case was strongly and diffusely positive for β-catenin in a nuclear and cytoplasmic pattern and CDX-2 in a nuclear pattern, supporting the role of the Wnt signaling pathway in such tumors. Furthermore, our case demonstrated the presence of few intralesional normal dendritic melanocytes, a rare finding1,24,25 but not unexpected, as melanocytes normally are present within the hair follicle matrix.
Pilomatrix carcinomas are aggressive tumors with a high risk for local recurrence and tendency for metastasis. In a study of 13 cases of pilomatrix carcinomas, Herrmann et al13 found that metastasis was significantly associated with local tumor recurrence (P<.0413). They concluded that the combination of overall high local recurrence and metastatic rates of pilomatrix carcinoma as well as documented tumor-related deaths would warrant continued patient follow-up, especially for recurrent tumors.13 Rapid growth of a tumor, either de novo or following several months of stable size, should alert physicians to perform a diagnostic biopsy.
Management options of pilomatrix carcinoma include surgery or radiation with close follow-up. The most widely reported treatment of pilomatrix carcinoma is wide local excision with histologically confirmed clear margins. Mohs micrographic surgery is an excellent treatment option.2,13-15 Adjuvant radiation therapy may be necessary following excision. Currently there is no consensus on surgical management, and standard excisional margins have not been defined.26 Jones et al2 concluded that complete excision with wide margins likely is curative, with decreased rates of recurrence, and better awareness of this carcinoma would lead to appropriate treatment while avoiding unnecessary diagnostic tests.2
Conclusion
We report an exceptionally unique case of early pilomatrix carcinoma with a discussion on the pathogenesis and molecular pathology of hair matrix tumors. A large cohort of patients with longer follow-up periods and better molecular characterization is essential in drawing accurate information about their prognosis, identifying molecular markers that can be used as therapeutic targets, and determining ideal management strategy.
