J.M. Theaker

Ber EP4 and epithelial membrane antigen aid distinction of basal cell, squamous cell and basosquamous carcinomas of the skin

Aims

Epithelial membrane antigen expression by the perineurial cell: further studies of peripheral nerve lesions

We have previously shown that a range of anti‐epithelial membrane antigen monoclonal antibodies show immunoreactivity with the perineurial fibroblast, both in normal nerves and within a range of common peripheral nerve tumours. We have extended these observations by studying a further collection of peripheral nerve lesions, including some which have previously been thought to have an origin from the perineurial cell. The results provide further evidence that these antibodies reliably stain perineurial cells and that in conjunction with antisera to S‐100 protein and neurofilaments, the relative contributions of the perineurial fibroblast, Schwann cell and neurone can be assessed within a nerve‐related tumour/lesion. The perineurial fibroblast is an important component of some peripheral nerve lesions.

Myofibroblastoma of breast: an immunohistochemical study

why it is usually found as an infecting agent in patients with increased susceptibility to infection such as the immunosuppressed. Many patients infected with Legionella are immunocompromised3 and there are previous case reports of an increased risk of infection in patients suffering from systemic lupus erythemato~us~. In addition, corticosteroid therapy enhances the risk of infection and appears to be a major factor in infection with Legionella micdadei5. Both of the present patients were taking regular steroid medication, but at low doses, and it seems likely that a combination of steroids, systemic lupus erythematosus and possibly an inherent genetic susceptibility all contributed to the acquisition of the dual infection and subsequent fatal outcome. Dual infection with Legionella pneumophila and Legionella micdadei has been previously reported6. Gastro-intestinal symptoms were the presenting complaint in these cases, a finding previously reported with Legionella3. It is unusual for Legionella infection to exhibit a miliary pattern and this finding, in conjunction with positively staining acid fast bacilli, resulted in a preliminary diagnosis of mycobacterial infection rather than Legionella. The microscopic features were more suggestive of Legionella than a mycobacterial infection but allowance has to be made for the modified inflammatory reactions seen in the immunocompromised. Diagnostic difficulties were compounded by the initial identification of Legionella pneumophila which is not acid fast and only later was there identification of acid fast Legionella micdadei. Despite extensive tests, the source of the infection in these two sisters could not be determined and it is likely that their infection was sporadic.

Cutaneous heterotopic meningeal nodules.

The clinical, light microscopic and immunohistochemical features of six cutaneous heterotopic meningeal nodules (primary, or type I, cutaneous meningiomas) are described. These are rare lesions of the scalp and back which generally present at birth or in childhood. They appear as small subcutaneous fibrous nodules, with no specific clinical features although they can be associated with abnormalities of spinal closure. Microscopically, they show a variable architecture but have similar cytological features. Important diagnostic features include psammoma and small collagenous bodies. An intimate relationship to nerves is seen in some cases, and this may be of significance with regard to the development of these lesions. As with intracranial meningiomas, there is widespread vimentin expression, and most cases show epithelial membrane antigen expression.

Digital pacinian neuroma: a distinctive hyperplastic lesion.

Neural tumours composed solely of Pacinian corpuscles or showing focal Pacinian differentiation are extremely rare and have only occasionally been reported in the literature. All such lesions to date have been benign. Three lesions are described herein which presented as painful digital masses in middle‐aged adults and which were composed of abnormal aggregates of morphologically mature Pacinian corpuscles and intervening small nerves. Only five similar cases have been previously recorded. Possible pathogenetic mechanisms of this unusual hyperplastic phenomenon are discussed.

The palisaded, encapsulated neuroma (solitary circumscribed neuroma)

We describe the clinical and pathological features of 41 palisaded encapsulated neuromas. They present as small, solitary, asymptomatic papules, predominantly on the face in middle age. No case had co‐existent neurofibromatosis or multiple mucosal neuromas. Histologically, they have distinctive features, consisting of a proliferation of Schwann cells and large numbers of axons within a perineurial derived capsule, permitting simple and reliable distinction from schwannomas and neurofibromas. Overall, the palisaded encapsulated neuroma accounts for approximately 25% of all nerve sheath tumours of the dermis. True schwannomas rarely occur in the dermis. Despite their original name, many cases are incompletely encapsulated and we support the recent proposal to rename these lesions solitary circumscribed neuroma.

Localized amyloidosis of the lower genitourinary tract: a clinicopathological and immunohistochemical study of nine cases

A series of nine cases of localized amyloidosis of the lower genitourinary tract are reported. The patients comprised six males and three females with an age range of 50‐79 years at initial presentation. Clinically and on cystoscopy, the lesions were often diagnosed as neoplasms. Histologically, seven cases had typical features of localized amyloid deposits, while two cases had an unusual appearance with a florid histiocytic and giant cell reaction. Using an immunoperoxidase staining method the deposits were non‐reactive with antibodies to serum amyloid A protein, prealbumin and β2 microglobulin, while equivocal immunoreactivity was seen with anti‐light chain antibodies.

Mucinous metaplasia of the penis

Mucinous metaplasia of the penis

Heterotopic glial nodules: a light microscopic and immunohistochemical study

The clinical, light microscopic and immunohistochemical features of 14 heterotopic glial nodules are described. In keeping with previous experience, most cases were located around the nose and had been present since birth. However, several lesions presented as cutaneous nodules elsewhere and, in some, presentation was delayed into childhood or even adulthood. The histological diagnosis is usually uncomplicated, but we draw attention to a variant with a markedly sclerosed stroma in which the glial cells are relatively inconspicuous. Such lesions tend to be found in older subjects and can cause problems in diagnosis. We emphasize the value of immunohistochemical demonstration of glial fibrillary acidic protein in the diagnosis of these lesions, especially the sclerotic variant. Other immunohistochemical features include the presence of axons in most cases and cell bodies in some, emphasizing the mixed nature of these lesions. A meningeal component could not be demonstrated immunohistochemically, even at the edge of the lesions.

Pagetoid spread into the rete testis by testicular tumours

Germ cell neoplasia of the testis can spread into the rete testis in a pagetoid manner, but this is less often recognized than vascular invasion or direct spread into the tunica albuginea. The rete testis was studied in 71 orchidectomy specimens: 47 with an untreated germ cell tumour, 18 with germ cell neoplasia after treatment with chemotherapy, and six with other tumours. Pagetoid spread into the rete testis was seen in 14 of the 47 cases of germ cell tumour. The cytology of the infiltrating cells was that of intratubular germ cell neoplasia. Hyperplasia of the rete testis was seen in six cases. In three of the four testes with untreated germ cell neoplasia and hyperplasia of the rete, neoplastic cells were seen in the hyperplastic rete epithelium. The two testes with extensive pagetoid involvement of the rete testis by intratubular germ cell neoplasia both had associated hyperplasia of the rete testis. Two of the 18 testes with germ cell neoplasia after chemotherapy had focal hyperplasia. Pagetoid involvement of the rete testis by intratubular germ cell neoplasia is common and may be a cause of hyperplasia of the rete testis.