Extensive Eosinophilic Infiltrates in the Epidermal Cyst Wall

Abstract

To the Editor: Extensive eosinophilic infiltrates in the epidermis often suggest bullous diseases, such as bullous pemphigoid, pemphigus foliaceus, and pemphigus vulgaris. We observed epidermal cysts with extensive eosinophilic infiltrates on scrotal examinations, which may be related to scrotal calcinosis. A 48-year-old man presented with 4 dermal nodules, which existed since he was 2 years-old. These nodules were pruritic at times with no other clinical inflammatory manifestation. The patient had developed spontaneous pneumothorax at 20 years of age not related to any allergic disease. Clinical examination revealed 4 hard dermal nodules less than 10 mm in diameter on the left side of the scrotum (Fig. 1). Epidermal cysts or scrotal calcinosis were suspected on clinical examination. Laboratory findings showed that serum calcium and phosphate levels as well as eosinophil counts were within normal limits. All 4 nodules were resected and subjected to histopathological examination, which revealed epidermal cysts (Fig. 2A). On histopathological examination, extensive eosinophilic infiltrates were found in all cyst walls and interspersed with keratin inside the cysts (Fig. 2B). In addition, numerous eosinophils and lymphocytes were found at the periphery of the cyst. In one of the cysts, granular basophilic material was found interspersed with keratin, which was determined to be calcium on von Kossa staining (Figs. 2C, D). No microorganism was observed on periodic acid–Schiff, Ziehl–Neelsen, and Grocott staining.FIGURE 1: Four hard dermal nodules on the left side of the scrotum.FIGURE 2: A, Scanning magnification revealed 4 epidermal cysts in the dermis (hematoxylin–eosin). B, Extensive eosinophilic infiltrates were found in all cyst walls and interspersed with keratin inside the cysts. Numerous eosinophils and lymphocytes were found at the periphery of the cyst (hematoxylin–eosin; original magnification, ×400). C, Granular basophilic material was found interspersed with keratin (hematoxylin–eosin; original magnification, ×400). D, von Kossa staining was positive for calcium interspersed with keratin (Kossa stain; original magnification, ×40).Many reports suggested that scrotal calcinosis develop in the setting of the epidermal cysts.1,2 Usually, this change is accompanied by a few inflammatory infiltrates.1,2 Based on these prior reports, extensive eosinophilic infiltration and calcium deposition in cysts may be coincidental. However, Novack et al3 highlighted the existence of some relationship between eosinophils and calcification by describing 2 cases with hypereosinophilic syndrome (HES) of prolonged course. A 35-year-old man with HES showed calcification of the femoral, iliac, radial, ulnar, common carotid, occipital, and posterior tibial vessels on x-ray examination. Histological examination of the surgically amputated toes showed perivascular eosinophilic cuffing with arteriolar thrombosis accompanying no arteriosclerotic changes. A 52-year-old man with HES showed diffuse arterial calcification of posterior tibial and digital vessels on x-ray examination. Although Novack et al3 stated that the cause of this calcification is unknown, they attributed it to injury and degenerative changes in peripheral arteries. Similarly, we speculate that eosinophilic infiltrates may cause calcification in cysts directly or indirectly via degenerative changes. Eosinophilic infiltrates in the epidermis are often found in early stages of bullous diseases.4 However, eosinophilic infiltration into the cornified layer through the epidermis is rare. Therefore, we first suspected the presence of some microorganism within the cysts; however, the special stains revealed nothing. The patient had no medical history of allergic diseases. In the present case, accumulation of extensive eosinophilic infiltrates in cysts is an enigma.