Giant pilomatricoma

Case contributed by Dr. Hugo Andrés Bustamante

Presentation

Chronic lesion on the posterolateral surface of the distal third of the right arm over the past 2 years with mild pain.

Patient Data

Age: 6 years
Gender: Male
X-ray

Lobulated, soft tissue lesión with calcification and the spotted pattern is present on the posterolateral surface of the right arm.

Ultrasound

A lesion with well-defined but irregular borders is seen in the US with echogenicity and acoustic shadow. The lesion appears vascular on the Power Doppler.

MRI

A soft tissue lesion is present on the posterolateral surface of the distal third of the right arm without invasion into muscular structures. Borders appear lobulated with heterogeneous signal on T1/T2 and STIR sequences with areas of perilesional edema and avid uptake of circulating paramagnetic contrast medium.

Pathology

Pilomatrixoma (Malherbe calcifying epithelioma)

a) dermal lesion of circular contour, cell nests with variable tonality, basophilic (**) to eosinophilic (*)

b) basophilic cells that mimic pillar matrix (*) in continuity with intermediate cells of stained nuclei (arrow) and "ghost" cells with discolored nuclei (arrowhead)

c) foreign body type reaction to focally calcified keratin sheets

Diagnosis

  • pilomatricoma (6.5cm larger diameter)
  • complete resection
  • multifocal dystrophic calcification
  • perilesional skin with segmental verruciform epidermal hyperplasia

Case Discussion

A 6-year-old male patient presented with a chronic lesion on the posterolateral surface of the distal third of the right arm for the past two years with mild pain. Complete resection of the lesion was completed with a histopathological report significant for arm tumor with multiple irregular fragments. The mass has a rough, bumpy surface with a brown-white stony appearance and dimensions of 3.5 x 2 x 1 cm, most suspicious for pilomatricoma.

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