Drug eruptions are common adverse reactions to drug therapy and are a frequent reason for consultation in clinical practice. Even though any medication can potentially cause an adverse cutaneous reaction, some drugs are implicated more commonly than others. Histologically, drugs can elicit a variety of inflammatory disease patterns in the skin and panniculus, no pattern being specific for a particular drug. The most common pattern elicited by systemically administered medications is the perivascular pattern. Psoriasiform or granulomatous patterns are rarely caused by medications. The usual histologic patterns of drug eruptions are discussed in this review using the basic patterns of inflammatory diseases. Clinicopathologic correlation is established for relevant patterns. However, the changes of drug-induced skin disease must be made considering clinical presentation, histopathological analysis, and course of the disease.

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Rosacea is classified into four clinical subtypes, namely erythematotelangiectatic, papulopustular, phymatous, and ocular. There is also a granulomatous variant, which is recognized in the rosacea spectrum. The objective of this study is to take a closer look at the different histopathologic patterns and cellular compositions seen in granulomatous rosacea and their correlation to the clinical presentation. Facial biopsies from patients previously identified with a clinical diagnosis consistent with rosacea, and who demonstrated a granulomatous infiltrate upon histopathologic examination, were reviewed and the results were correlated to the clinical presentation. Four distinct histopathologic granulomatous patterns were identified, namely nodular, perifollicular, diffuse, and a combined perifollicular and nodular patterns. The clinical presentation varied greatly among patients and failed to correlate to the microscopic findings. The varied clinical features seen in our study favors the theory that granulomatous rosacea is not a clinical subtype of rosacea per se, but a distinct histological variant, which can be found in most of its clinical spectrum.

Nodular mucinosis is an extraordinary stromal lesion of the breast. The usual clinical presentation is that of an oozing, slow-growing, soft, non-tender, lobulated mass in the subareolar region. Histologically, it is a non-encapsulated myxoid/mucinous lesion with a sparse infiltrate of spindle cells within a collagenized stroma. The histogenesis of nodular mucinosis is undetermined but the pattern of staining of the spindle cells suggests it might be of myofibroblastic origin. We herein report for the first time in the English literature a case of nodular mucinosis occurring in a supernumerary nipple. We also discuss the main differential diagnoses and review the literature of previously published cases of this entity.

Distinguishing primary cutaneous adnexal carcinoma from metastatic carcinoma of unknown primary can be a diagnostic challenge due to the frequent overlap of histologic and immunohistochemical features. A 58-year-old man presented with a tender, indurated plaque on axillary skin. Biopsy revealed infiltrating atypical cells throughout the dermis, without connection to the epidermis. Tumor cells had a histiocytoid appearance and displayed mild pleomorphism. The tumor was discohesive and had areas with a single file pattern. Signet ring cells were also present. Cells were reactive with CK7, CK5/6, p63, GATA3, GCDFP-15 and Her 2-neu. Additional studies were negative, including TTF-1, CDX2, E-cadherin, mammaglobin, estrogen receptor and progesterone receptor. Thorough clinical and radiologic evaluation failed to identify an occult primary extracutaneous malignancy; however, regional lymphadenopathy, widespread osteoblastic lesions and multiple subcentimeter liver hypodensities were noted. Considering the clinical and histopathologic features, the diagnosis of primary cutaneous histiocytoid carcinoma with distant metastasis was favored.