Yonago Acta medica 2007;50:65–68

Pigmented Neuroﬁbroma in the Appendix Diagnosed withColonoscopy
Akemi Ohnishi, Yukisato Kitamura, Masako Kato, Yoshitomo Kawamura* andKazuhiko Hayashi
Division of Molecular Pathology, Department of Microbiology and Pathology, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8503 and *Kawamura Clinic, Hofu
747-0064 Japan

Pigmented (melanotic) neurofibromas in the appendix are extremely rare. To ourknowledge, this is the first case of appendiceal pigmented neurofibroma in a patient
without neuroﬁbromatosis 1, which was colonoscopically diagnosed. Histologically, thetumor cells were spindle shaped with indistinct cell borders. The tumor cells had cytoplasms with many gray-brown pigments. Immunohistochemical examinations showedthat the tumor cells were strongly positive for S-100 protein, and were focally positive for
Melan-A. They were also diffusely positive for Leu7 (CD57), or neuron-speciﬁc enolase(NSE). No positive expression of tumor cells was observed for -smooth muscle actin,desmin, CD34, c-kit, HMB45. No mitotic ﬁgures were observed. The Ki-67 labelingindex was less than 1%. The tumor was thus diagnosed as primary pigmented neuroﬁbroma in the appendix. In the present case, tumor cells showed no mitotic activity anda Ki-67 index of less than 1%, suggesting a benign tumor.
Key words: appendiceal tumor; pigmented neuroﬁbroma

Pigmented (melanotic) neurofibromas are rare(Fetsch et al., 2000). According to the Armed
Forces Institute of Pathology, pigmented neuroﬁbromas constitute less than 1% of all neuroﬁbromas (Sharon et al., 2001). One case of diffuse
neurofibroma in the appendix associated withneurofibromatosis 1 (von Recklinghausen’s disease) was reported (Miettinen et al., 2001). The
present article reports a colonoscopically diagnosed pigmented neurofibroma in the appendix.
To our knowledge, this is the ﬁrst case of appendiceal pigmented neuroﬁbroma in a patient without
neuroﬁbromatosis 1.

Patient Report
Clinical summary

A 59-year-old Japanese man, who had stools withoccasional signs of blood on occasion, underwent
colonoscopic examination. A doughnut-like protruding tumor, slightly whitish in color and about
1.5 cm in diameter, was found in the appendiceal
oriﬁce (Fig. 1). However, there were no remarkable abnormalities upon physical or laboratory
examinations.
Pathological ﬁndings

Histopathological evaluation of the biopsy specimen revealed pigmented neurofibroma in the65

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appendix. Histologically, the tumor cells proliferated in the lamina muscularis mucosae andsubmucosal tissues (Fig. 2). The tumor was composed of spindle shaped cells with indistinct cellborders. No mitotic ﬁgures were observed (Fig.
2). Most of the tumor cells had many gray-brown
pigments within cytoplasms, which stained blackwith Fontana-Masson stain for melanin (Fig.
3). Immunohistochemical studies of the tumor
cells were performed for S-100 protein, Melan-A,Leu7 (CD57), neuron-speciﬁc enolase, -smoothmuscle actin, desmin, CD34, c-kit and HMB45.
The Ki-67 labeling index was less than 1%. The
results of the immunohistochemical studies aresummarized in Table 1.
Fig. 1. Endoscopic ﬁnding. There is a doughnut-like
protruding tumor at the appendiceal oriﬁce. The tumor
is slightly whitish in color and 1.5 cm at its greatest dimension. Macroscopically, the surface of the tumor issmooth. Bar = 1 cm.

Discussion
Sometimes appendiceal tumors are found when
the patient has symptoms in the appendix orthrough intussusception (Abramson et al., 1997).
In our case, there were no appendix symptoms

Fig. 2. Tumor cells proliferate in the lamina muscularis mucosa. The tumor is composed of spindle-shaped cells
and round cells with indistinct cell borders. The cells have clear eosinophilic cytoplasms. The nuclei of the tumor
cells are characteristically elongated and wavy (hematoxylin and eosin stain). Bar = 20 μm.

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