BACKGROUND: Pilomatrixoma (pilomatrixoma, calcifying epithelioma of Malherbe) is a relatively uncommon, benign neoplasm arising from the skin adnexa. The tumor can cause diagnostic difficulty not only for the clinician but also for the cytologist. CASE: A 62-year-old woman presented with a right submandibular swelling of 4 months' duration. The clinical findings were highly suspicious for malignancy. A fine needle aspiration biopsy was performed. Three preliminary differential diagnoses were offered: mucoepidermoid carcinoma of the submandibular salivary gland, squamous cell carcinomatous deposit in a submandibular lymph node and calcifying odontogenic tumor. Computed tomography demonstrated no bony lesion. No primary site of squamous cell carcinoma could be identified. An excisional biopsy of the swelling was performed, and the histologic diagnosis of pilomatrixoma was made. CONCLUSION: The cytologic presentation of pilomatrixoma of the right submandibular region can masquerade as that of a malignant tumor, in this case mucoepidermoid carcinoma, squamous cell carcinoma or odontogenic tumor. This case delineates the cytomorphologic features of pilomatrixoma that may mimic carcinoma.

Clinicopathologic study of eyelid pilomatrixoma: the experience of the "Hospital Universitário Prof. Edgard Santos".Arq Bras Oftalmol. 2007 May-Jun;70(3):501-3.

PURPOSE: To report the experience with eyelid pilomatrixoma during 30 years in a university hospital. METHODS: A review of the Ophthalmic Pathology Laboratory at the "Hospital Universitario Prof. Edgard Santos", was conducted to identify eyelid tumor cases from 1974 to 2004. After identification of pilomatrixoma cases, a chart review retrieved data regarding gender, age, duration of symptoms, gross aspect, anatomic localization and clinical diagnosis. The hematoxilin and eosin stained sections were reviewed. RESULTS: Of a total of 621 eyelid tumors, four (0.64%) were pilomatrixomas. Three patients were male. The mean age at diagnosis was 25 years (from 8 to 54). Mean duration of symptoms was 5 months (from 2 to 12). In three cases the lesion was located in the inferior lid. Only one patient had a correct clinical diagnosis. Two cases exhibited a pseudo-capsule on histology. The case with 12 months of history was composed mainly of shadow cells. Foreign body reaction was seen in all cases, calcification in only one. CONCLUSION: This is a very rare benign tumor of young patients. Due to its rarity and variable clinical presentation, clinical misdiagnosis is common.