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Delayed Arrival

March 01, 2005
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Pathology and Diagnosis


The pathology of both specimens showed epithelioid tubercles containing foreign body type giant cells and the presence of birefringent refractile and polarizable material.

Patient #1 (click image to enlarge)

Patient #2 (click image to enlarge)

DIAGNOSIS: Silica Granulomas

Silicon dioxide, or silica, makes up a variety of common minerals including quartz, tridymite, cristobalite, agate, and onyx. Hundreds of other minerals are composed of more complex silicates, weathering of which may result in liberation of silica in ultrafine particulate colloidal form. Silicates are present in a variety of substances, which may act as foreign bodies after injury, including brick, cement, dirt, rock and sand.

Granulomas due to silica typically have extremely prolonged latency averaging 10 years, and in some cases as long as 59 years.1 The forehead, lip and elbow are common sites of formation.

One theory for this latency was propounded by Shelley and Hurley.2 They showed that intradermal injection of various-sized particles of silica produced granulomatous response only when present in fine colloidal form, findings consistent with studies of an earlier researcher. They theorized that the long latency of silica granulomas resulted from a slow process of weathering of silicates in tissue, eventually resulting in colloidal silica, capable of triggering non-allergic granulomatous inflammation.

Birefringent foreign material is not specific for silica granulomas. In a recent study of sarcoidosis, 50% of biopsies evidenced this finding.3 In most of these cases the clinical morphology sugggested sarcoidosis, reinforcing the importance of the overall clinical picture in diagnosis.


1. Eskeland G, Langmark F, Husby G. Silicon granuloma of skin and subcutaneous tissue. Acta Pathol Microbiol Scand A Suppl. 1974;248:69-73

2. Shelley W, Hurley H. The pathogenesis of silica granulomas in man: a non-allergic colloidal phenomenon. J Invest Dermatol 34:107-123.

3. Ball NJ, Kho GT, Martinka M. The histologic spectrum of cutaneous sarcoidosis: a study of twenty-eight cases. J Cutan Pathol. 2004;31:160-8.

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