S10C4P2-Lipogranuloma

S10C4P2-1: At this magnification, it is tempting to characterize all the symmetrically rounded spaces as lipocytes and to attribute the irregular spacing of these rounded spaces to a physical displacement of lipocytes by the infiltrates of epithelioid histiocytes. The rounded spaces vary in size. Not all of the rounded spaces are associated with the eccentric nuclei of viable lipocytes; those that are not nucleated are not viable lipocytes; they are fat-filled defects. They represent dead lipoctyes or have formed as a result of the release of lipid into the tissue following the death of lipocytes. In the area outlined by blue arrows, a lipid-rich cyst has evoked a granulomatous response; the patterns are lipogranulomatous. This is a common, and basic, response to damage of fat and death of lipocytes; it is a basic response of tissue to free lipids, whether exogenous or endogenous (lipogranulomatous panniculitis).

S10C4P2-2: To the right, there is a zone of fibrosis with three lipogranulomas. The three granulomas are rounded in outline; they show a central, rounded space and a peripheral zone of palisaded histiocytes. To the left, spaces, that vary in size, are irregularly distributed in a fibrous, somewhat hyalinized matrix. There are spotty infiltrates of lymphocytes.

S10C4P2-3: A lipogranuloma is represented to the left; palisades of histiocytes border the rounded defect (fat cyst). The defects to the right vary in size; each is outlined by a distinct membrane. The defects are not associated with an eccentric nucleus as would be the case, if the defects represented viable lipocytes. The neighboring fibrous tissue is loosely fibrillated. The inflammatory infiltrates are composed of lymphocytes and histiocytes, with occasional plasma cells.

S10C4P2-4: This is a variation of the pattern of lipogranulomatous panniculitis. Defects, which are rounded in outline, are fairly regularly, and loosely, spaced in a delicate, fibrous matrix. They have the general size and the characteristics of lipocytes; some are collapsed and irregular in outline (lipocytes that are atrophic lose lipids from the cytoplasm and become smaller; these atrophic forms tend to become somewhat crenated in outline). Many of the defects, which are lipocyte-like in size and shape, are outlined by a single layer of flattened cells. These flattened cells are histiocytes. Each unit, so defined and consisting of a central rounded defect and a peripheral row of flattened histiocytes, is a small lipogranuloma. This is an example of focal changes in a lesion in which the patterns, overall, were in keeping with lupus panniculitis (LE profundus ). The patterns are both lipogranulomatous and lipoatrophic.

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