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Cutaneous silica granuloma: a lesion that might be clinically underdiagnosed

European Journal of Dermatology. Volume 15, Number 3, 194-5, May-June 2005, Clinical report

Summary

Author(s) : Gonca Boztepe, Mohammad Rakhshanfar, Gül Erkin, Özay Özkaya, Sedef Şahin, Hacettepe University Faculty of Medicine, Department of Dermatology Sihhiye, 06100, Ankara, Turkey Fax: (+90) 312 309 7265., Hacettepe University, Faculty of Medicine, Department of Pathology, Sihhiye, 06100, Ankara, Turkey.

Summary : Cutaneous silica granuloma is a poorly understood, uncommon condition. There have been relatively few reports of cutaneous silica granuloma despite the well-known ubiquitous nature of silica in the environment. The characteristic latency period between the time of silica exposure to the time of clinical onset of granuloma, lack of clear-cut histories of exposure in most cases and likelihood of spontaneous resolution, may challenge the diagnosis. Thus, cutaneous silica granuloma might be a lesion that is often underdiagnosed. Here we describe a patient with characteristic findings of cutaneous silica granuloma.

Keywords : silica granuloma, foreign body granuloma, polarized light microscope, granulomatous dermatitis

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ARTICLE

Auteur(s) :, Gonca Boztepe^1,*, Mohammad Rakhshanfar¹, Gül Erkin¹, Özay Özkaya², Sedef Şahin¹

¹Hacettepe University Faculty of Medicine, Department of Dermatology Sihhiye, 06100, Ankara, Turkey Fax: (+90) 312 309 7265.
²Hacettepe University, Faculty of Medicine, Department of Pathology, Sihhiye, 06100, Ankara, Turkey

accepté le 5 Avril 2004

Cutaneous silica granuloma (CSG) is a poorly understood, rare condition that is occasionally encountered after trauma. It was first described by Shattock in 1916, when he performed a biopsy on a lip tumor that has arisen in a scar resulting from an injury that had happened 11 years previously [1]. Since then, relatively few additional cases have been reported.Most patients with CSG lack clear-cut histories of traumatic exposure [2]. Even if they recall an injury, the characteristic latency period until the onset of granuloma challenges the diagnosis [3].It is usually presented clinically as erythematous, firm, non-tender, dermal or subcutaneous nodules. Non-caseating granulomatous infiltration with lymphocytes, histiocytes, and giant cells constitute the histopathologic picture of CSG, which might easily be misinterpreted as sarcoidosis or cutaneous leishmaniasis unless such specimens are routinely examined under polarized light microscope [4]. Birefringent particles visualized under polarized light microscope lead to a proper diagnosis of CSG, which may further be confirmed by energy-dispersive X-ray analysis. Here we describe a patient with characteristic clinical and microscopic findings of CSG.

Case

A 38-year-old male patient presented with a 1-year history of a pruritic nodular lesion on the left forearm, which had been gradually enlarging in size. The patient’s past history was unremarkable except that he had been working at a glass factory until 4 years previously. He did not recall any injury to the forearm during the time he worked in the factory.

Examination of the skin revealed a 1.5 × 1.5 cm firm, erythematous, non-tender nodule with a pearly and telangiectatic surface on the left forearm ( (figure 1) ). No palpable regional lymphadenopathy was noted. A skin punch biopsy demonstrated diffuse granulomatous infiltration involving the whole dermis with abundant giant cells and sparse lymphocytes ( (figure 2) ). Refractile particles were visualized within these giant cells ( (figure 3) ). These particles were birefringent under polarized light. The lesion was then totally excised. This resulted in total resolution without recurrence.

Discussion

Silica granuloma occurs after the introduction of silicon dioxide (silica) into the skin, usually after an injury. Silica is one of the most abundant elements in the earth’s crust. It is present in sand, glass, granite, mica, cement, brick and asbestos. The most common form of silica is quartz, which is a constituent of nearly every rock. There is often a characteristic latency period between the time of silica exposure and the time of clinical onset of granuloma. This has ranged from less than 1 year to more than 50 years with a mean interval of approximately 10 years, in published records [2]. Besides, most recorded instances of silica granuloma do not present clear-cut histories of trauma.

Single or multiple erythematous, firm, non-tender, dermal or subcutaneous nodules are the most common clinical presentation of silica granulomas [5]. There have also been reports accompanied by regional lymphadenopathy, with silica present in the lymph nodes on histological examination [6, 7].

Biopsy specimens characteristically demonstrate a histological picture of a foreign body granuloma with abundant giant cells surrounding numerous crystalline structures. Cases of more organized non-caseating epitheloid granulomas may look extremely like cutaneous sarcoidosis [2, 4]. Polarized light microscopy is essential for a proper differential diagnosis of silica granuloma and sarcoidosis. The diagnosis of silica granuloma can further be confirmed by energy-dispersive X-ray analysis [2, 8].

The pathogenesis of silica granuloma is poorly understood. According to one of the two most supported theories, silica in the tissue is hydrolyzed by the interstitial fluids to a colloidal state which after many years triggers a granulomatous response [9]. The second theory is based on the idea that silica granulomas represent a delayed type of hypersensitivity [5].

Surgical excision appears to be the treatment of choice for silica granuloma [8]. Alternative treatments include intralesional steroid injections [4], systemic steroids, irradiation, and antibiotics. However, reports of spontaneous resolution of silica granuloma somehow obscure the effectiveness of these therapies. It is mentioned in the literature that if spontaneous resolution is to be observed, it occurs between 1 to 12 months [8].

In our case, despite negative history of an injury to forearm, exposure to silica at the glass factory, the presence of latency period and classical clinical as well as microscopic features were the clues that had led to the diagnosis.

Concerning silica granuloma, the questions of why it is so rarely seen despite its ubiquitous nature in the environment, and what are the roles of clinical underdiagnosis and spontaneous resolution on its rarity, are yet to be elucidated.

References

1 Shattock SG. Pseudotuberculoma silicotum of the lip. Proc R Soc Med 1916; 10: 19-21.

2 Mowry RG, Sams M, Caulfield JB. Cutaneous silica granuloma. A rare entity or rarely diagnosed? Report of two cases with review of the literature. Arch Dermatol 1991; 127: 692-4.

3 Finley J, Knabb J. Cutaneous silica granuloma. Plast Reconstr Surg 1982; 69: 340-3.

4 Kaya TI, Kokturk A, Polat A, Anadolu R, Tursen U, Ikizoglu G. Cutaneous silica granuloma in a child. Pediatr Dermatol 2003; 20: 40-3.

5 Rank BK, Hicks JD, Lovie M. Pseudotuberculoma granulosum silicoticum. Br J Plast Surg 1972; 25: 42-8.

6 Kuchemann K, Holm R. Unusual silica granulomas of skin with masssive involvement of axillary lymph nodes. Pathol Res Pract 1979; 164: 198-206.

7 Morgan RJ. Cutaneous silica granuloma. Cutis 1986; 38: 95.

8 Bovenmyer DA, Landas SK, Bovenmyer JA. Spontaneous resolution of silica granuloma. J Am Acad Dermatol 1990; 23: 322-4.

9 Shelley WB, Hurley HJ. The pathogenesis of silica granulomas in man: a non-allergic colloidal phenomenon. J Invest Dermatol 1960; 34: 107-22.