Invasive Features in Granular Cell Tumors of the Skin
Invasive Features in Granular Cell Tumors of the Skin
Background Incidental finding of vascular invasion has been described in some benign granular cell tumours. Malignancy in granular cell tumours is excessively rare and its assessment relies on necrosis and cytological criteria.
Aims To assess histopathological invasive features, particularly vascular invasion, in a large series of granular cell tumours of the skin.
Methods 119 granular cell tumours of the skin were collected in 114 patients between 2001 and 2011. Histopathological and epidemiological data were collected. Five step sections and one orcein staining were performed in all cases.
Results Mean age of the patients was 43.7±18 years. Granular cell tumours were multiple in 7% of patients. They were classified as benign in 111 cases, and atypical in eight cases. No malignant granular cell tumour was present. Tumours had 1.48±1.3 cm mean diameter, showed peripheral invasive growth pattern in 71% of cases, had a mean depth of 8.8±4.7 mm, and reached the subcutis in 66% of cases. Infiltration of arrector pili muscle occurred in 23% (95% CI 16% to 32%), and perineural spread in 66% (95% CI 56% to 74%) of cases. Vascular invasion occurred in 23% (95% CI 16% to 32%) of cases, with subendothelial layers infiltration or vascular obliteration. No intraluminal embolus was found. No association was found between vascular invasion and clinical outcome.
Conclusions Histopathological features of local invasion are frequent in otherwise benign granular cell tumours. Vascular invasion consists of an infiltration of the subendothelial layers, without intraluminal cells, and may not be considered as a marker of adverse prognosis.
Granular cell tumour is a fairly common tumour of probable peripheral nerve sheath differentiation but distinctive from schwannomas. It is localised mainly in the dermis, subcutis or submucosa of various locations (respiratory, digestive or urinary tract). It is benign in the vast majority of cases, but rare malignant cases have been documented, behaving as high grade sarcomas and having about 60% risk of causing death. Malignancy is assessed on the basis of histopathological criteria proposed by Fanburg-Smith et al, namely the presence of necrosis, cellular spingling, vesicular nuclei with large nucleoli, increased mitotic activity, high nuclear to cytoplasmic ratio, and pleomorphism. Tumours with at least three of the six listed morphological criteria have been classified as malignant, whereas those having one or two criteria are termed as atypical.
Granular cell tumours tend to be poorly circumscribed, with cells disposed in ribbons or nests divided by fibrous connective tissue. A plexiform growth pattern has also been described. The granular cells are said to be frequently in close association with small nerves, encompassing or replacing them almost entirely. The exact frequency of perineural spread has not been thoroughly evaluated in the literature. The granular cells can also involve or replace the musculature, growing along muscle fibres or extending within the sarcolemmal sheath in striated muscle. Granular cell tumours have also been described in smooth muscle tissue, in heart muscle, or in fibrous tissue such as tendons, fascia or ligaments.
Incidental finding of vascular invasion has been described in four benign granular cell tumours out of five, found with the help of orcein staining for elastic tissue. Such a finding was not described in the seminal paper about malignancy criteria in granular cell tumour, nor in major textbooks. Vascular invasion was also documented in one case of granular cell tumour on the penis, where the tumour behaved in a benign fashion. From the few cases reported it is not possible to obtain an estimate of the incidence of vascular invasion in granular cell tumour, or evaluate its association with other invasive findings.
In this work, we assessed the invasive features, particularly vascular invasion, in a series of 119 granular cell tumours of the skin.
Abstract and Introduction
Abstract
Background Incidental finding of vascular invasion has been described in some benign granular cell tumours. Malignancy in granular cell tumours is excessively rare and its assessment relies on necrosis and cytological criteria.
Aims To assess histopathological invasive features, particularly vascular invasion, in a large series of granular cell tumours of the skin.
Methods 119 granular cell tumours of the skin were collected in 114 patients between 2001 and 2011. Histopathological and epidemiological data were collected. Five step sections and one orcein staining were performed in all cases.
Results Mean age of the patients was 43.7±18 years. Granular cell tumours were multiple in 7% of patients. They were classified as benign in 111 cases, and atypical in eight cases. No malignant granular cell tumour was present. Tumours had 1.48±1.3 cm mean diameter, showed peripheral invasive growth pattern in 71% of cases, had a mean depth of 8.8±4.7 mm, and reached the subcutis in 66% of cases. Infiltration of arrector pili muscle occurred in 23% (95% CI 16% to 32%), and perineural spread in 66% (95% CI 56% to 74%) of cases. Vascular invasion occurred in 23% (95% CI 16% to 32%) of cases, with subendothelial layers infiltration or vascular obliteration. No intraluminal embolus was found. No association was found between vascular invasion and clinical outcome.
Conclusions Histopathological features of local invasion are frequent in otherwise benign granular cell tumours. Vascular invasion consists of an infiltration of the subendothelial layers, without intraluminal cells, and may not be considered as a marker of adverse prognosis.
Introduction
Granular cell tumour is a fairly common tumour of probable peripheral nerve sheath differentiation but distinctive from schwannomas. It is localised mainly in the dermis, subcutis or submucosa of various locations (respiratory, digestive or urinary tract). It is benign in the vast majority of cases, but rare malignant cases have been documented, behaving as high grade sarcomas and having about 60% risk of causing death. Malignancy is assessed on the basis of histopathological criteria proposed by Fanburg-Smith et al, namely the presence of necrosis, cellular spingling, vesicular nuclei with large nucleoli, increased mitotic activity, high nuclear to cytoplasmic ratio, and pleomorphism. Tumours with at least three of the six listed morphological criteria have been classified as malignant, whereas those having one or two criteria are termed as atypical.
Granular cell tumours tend to be poorly circumscribed, with cells disposed in ribbons or nests divided by fibrous connective tissue. A plexiform growth pattern has also been described. The granular cells are said to be frequently in close association with small nerves, encompassing or replacing them almost entirely. The exact frequency of perineural spread has not been thoroughly evaluated in the literature. The granular cells can also involve or replace the musculature, growing along muscle fibres or extending within the sarcolemmal sheath in striated muscle. Granular cell tumours have also been described in smooth muscle tissue, in heart muscle, or in fibrous tissue such as tendons, fascia or ligaments.
Incidental finding of vascular invasion has been described in four benign granular cell tumours out of five, found with the help of orcein staining for elastic tissue. Such a finding was not described in the seminal paper about malignancy criteria in granular cell tumour, nor in major textbooks. Vascular invasion was also documented in one case of granular cell tumour on the penis, where the tumour behaved in a benign fashion. From the few cases reported it is not possible to obtain an estimate of the incidence of vascular invasion in granular cell tumour, or evaluate its association with other invasive findings.
In this work, we assessed the invasive features, particularly vascular invasion, in a series of 119 granular cell tumours of the skin.