Postirradiation pseudosclerodermatous panniculitis with involvement of breast parenchyma: a dramatic example of a rare entity and a pitfall in diagnosis.

Postirradiation pseudosclerodermatous panniculitis is a rare complication of external beam radiotherapy. This inflammatory process typically presents as an erythematous indurated plaque in a previously irradiated region of skin. To date, 13 cases have been reported worldwide. We present a case of a 70-year-old female who received breast irradiation following conservation surgery for invasive breast carcinoma. In her third year of follow-up, she developed an enlarging mass, involving the subcutis and underlying breast tissue, associated with mammographically detected coarse calcifications and density, at the surgical site. This was deemed highly suspicious of recurrent malignancy. Following several benign needle core biopsies, she had an excision of the mass. This revealed a lobular panniculitis and irradiation-induced vascular changes affecting subcutaneous fat and underlying breast tissue. This is the 14th reported case of this rare entity. It is unique in the degree of involvement, affecting breast parenchyma as well as subcutaneous fat, and in its corresponding dramatic clinical and radiographic manifestations.